Releasable stores (armament such as bombs, rockets, flares, and the like) for manned aircraft are usually positioned on proprietary carriages and release mechanisms that are designed to integrate with a conventional piloted aircraft. These systems are highly specific to the aircraft and are not readily adaptable to other aircraft.
On the other hand, small, remotely controlled, pilotless aircraft are much lighter in weight than conventional aircraft and are designed primarily for surveillance, but can also be adapted to carry releasable stores. The number and type of pilotless aircraft and other drones are quite large compared to the number of conventional manned aircraft in the military. Release and armament systems for each of these aircraft would normally be designed on an aircraft-by-aircraft basis, thus resulting in substantial design time and expense associated with adapting the unmanned aircraft to carry stores.